After an oil well has been partly drilled and suspected producing formations have been penetrated, it is necessary to make various tests to determine production possibilities of various formations. One of the test techniques involves the use of a tool which is known as a formation tester. An exemplary formation tester is set forth in U.S. Pat. Nos. 4,375,164 and 4,593,560 assigned to assignee of the present disclosure. As set forth in those disclosures, the tool is adapted to be lowered into the well bore, supported on an armored logging cable enclosing certain conductors for providing surface control for the tool. The logging cable extends to the surface and passes over a sheave and is spooled on a reel or drum. The conductors in it connect with suitable surface located power supplies, controls, and recorder. The formation tester is lowered to a specified depth in a well. At that elevation, a backup shoe is extended on one side of the formation tester and formation testing apparatus is extended diametrically opposite into the formation of interest. The equipment so extended normally includes a surrounding elastomeric sealing pad which encircles a smaller extendable snorkel which penetrates a formation as the formation will permit, up to a specified depth. The snorkel is ideally isolated from fluid and pressure in the well to be able to test the formation. The snorkel is extended into the formation to enable direct fluid communication from the formation into the tool. Moreover, it is isolated from invasion of the well borehole fluid and pressures therein to permit a pressure sensor to obtain formation pressure. Further, a sampling chamber elsewhere in the formation tester can be selectively connected through the snorkel by suitable valves to obtain delivery of a fluid sample from the formation. The fluid sample typically may include a relatively small sample which is a pretest sample, and if that is acceptable, a larger sample can be drawn through the snorkel. Various pretest and sample volumes are selected and determined under control from the surface.
Testing procedures require a substantial interval. For instance, isolation steps must be undertaken to assure that the formation tester properly obtains data from a single formation without invasion of other well fluids from different strata. These procedures involve extension and retraction of the packer and snorkel described above. These steps are normally accompanied by the extension of certain backup shoes which set backup shoes on the opposite side of the formation tester in the borehole. Thus, the references noted above describe apparatus which extends the snorkel on one side of the tool body and which extend backup pistons on the opposite side to assure that adequate force is delivered to position the snorkel in the formation of interest.
These procedures require some time to execute. Delay is costly in the performance of such downhole test procedures and equipment. The delay that is encountered in performing such tests translates into added cost. While the cost of rental of a formation tester can be negligible, a far greater cost is the rig time involved during which time the testing procedures are carried out. Ideally, test procedures are conducted as rapidly as possible to assure that the tests are conducted at a minimum cost. As a practical matter, rig time is an increment of cost which can substantially exceed the cost of rental of a formation tester. For these reasons, it is desirable that the formation tester operate as rapidly as possible.
One of the steps carried out by the formation tester is extension of the snorkel and surrounding pad which achieves a seal to isolate the formation. Additionally, backup pistons are extended, thereby assuring that backup shoes are anchored in the well borehole. After this equipment has been extended and after the formation test procedure has ended, the extended equipment is retracted. The snorkel is pulled in and the seal around the elastomeric gasket is normally broken. The backup shoes extended on the opposite side of the testing tool are also retracted.
The present invention is directed to an improved system including a hydraulic circuit within the formation tester which assures that the foregoing movements are carried out as rapidly as possible. That is, the formation testing apparatus is extended and retracted as quickly as possible. This improved apparatus provides a means and mechanism whereby more rapid extension is obtained. This cuts down on the time in which the formation tester is in the borehole. This thereby reduces the test duration and reduces rig time costs. This also reduces the possibility of sticking. It also assures that the extended and retracted equipment is quickly and properly seated to be subsequently retracted. With the foregoing in view, the present apparatus is summarized as a valving system including solenoid valves cooperative with a speed-up mechanism thereby assisting rapid operation of the equipment in the formation tester. Extension of the apparatus is speeded up so that the formation tester can be moved as quickly as possible from location. Further objects and advantages of the present disclosure will become more readily apparent upon consideration of the description of the preferred embodiment set forth below in conjunction with the drawings.